Rocky shores, UK

Description

The UK’s expansive coastline, which is well over 6,000 kilometres long, varies dramatically and presents a number of different rocky habitats, ranging from calm, sheltered coves and rocky beaches to tall, imposing cliffs. Within each of these rocky habitats the conditions are highly dynamic, due to the ever-changing tides (1) as well as additional environmental factors such as temperature and wind (2). Rocky shores are formed when waves erode softer rocks, leaving harder rocks exposed (3).

UK rocky shores fact file

Description

The UK’s expansive coastline, which is well over 6,000 kilometres long, varies dramatically and presents a number of different rocky habitats, ranging from calm, sheltered coves and rocky beaches to tall, imposing cliffs. Within each of these rocky habitats the conditions are highly dynamic, due to the ever-changing tides (1) as well as additional environmental factors such as temperature and wind (2). Rocky shores are formed when waves erode softer rocks, leaving harder rocks exposed (3).

Marine habitats are often divided into several zones, which are based on their position in relation to the tide. The sublittoral zone is the area of the shore which lies below the low tide line, and is therefore permanently submerged. This is the most stable environment within a rocky shore habitat, and also one of the richest, sustaining an abundance of different marine species (4).

The intertidal zone is the area between the high and low tide lines which is intermittently submerged or exposed to the air depending upon the position of the tide. Areas closer to the sea are the first to be submerged as the tide rises and the last to be exposed as it ebbs, and therefore spend a greater proportion of time fully submerged. Species present throughout the intertidal zone must be able to survive both in and out of sea water (4), and they vary in form and function according to their distance from the sea (2).

As the tide goes out, pools of seawater remain on uneven rocks. Rock pools are temporarily separated from the sea, with the pools further away being isolated for longer. The conditions in these small microhabitats are often harsh, with evaporation and rain causing the concentration of salt in the water (the salinity) to fluctuate dramatically. The temperature and oxygen levels can also vary immensely depending on sun exposure and plant activity (5). Species that live in rock pools must be able to cope with an ever-changing and often relatively extreme environment (5)(6), yet the pools frequently sustain a host of plants, crustaceans, anemones and fish (6).

Seaweed and other marine debris is deposited at the point reached by the highest tide (7), called the springtide (4), forming the strandline. This plant matter supports a variety of small invertebrates, which in turn are prey items for larger animals such as birds and small mammals (7).

Further up the shore, the splash zone is the area above the high tide point that is rarely, if ever, submerged by the water, although the rocks will occasionally be soaked by wave splashes. This harsh environment is unable to sustain as much diversity of life as the areas closer to the sea. However, some species such as lichens and sea slaters are able to survive there (4).

Range

Biodiversity

Rocky shores are rich in marine biodiversity, with an impressive range of species occupying the different marine zones down the shore. As a fully marine environment, the sublittoral zone can sustain a wide variety of species. Many of the species inhabiting the intertidal zone are specifically adapted to be able to live both in and out of the sea, and therefore cannot be found elsewhere (2).

Biodiversity generally decreases further away from the sea, with only a few species of lichen being able to survive on rocks in the splash zone. Marine plant material deposited in strandlines, however, provides important habitat for small invertebrates and birds further away from the sea (7).

Rocky shores provide food for a variety of different native and migratory birds including gulls, waders, terns, eiders and kittiwakes (8). Oystercatchers (Haematopus ostralegus) prowl the rocky shores looking for limpets, crabs and mussels. Cliff shorelines are used as rest stops and breeding grounds for bird species that dive for fish out at sea, such as the puffin (Fratercula arctica)(10).

Rocky shores are home to several species of fish, including lumpsuckers, butterfish and goby (8). The giant goby (Gobius cobitis) can be found in rock pools on the western part of England’s southern coast (11).

Explore the biodiversity of UK rocky shores:

Threats

Rocky shores are vulnerable to various types of pollution, including oil pollution which mainly comes from waste rather than oil spills. Oil smothers species living on rocks near the shore and can also poison rock pools. Toxic chemicals from boats (3), as well as leached pesticides and herbicides, can also have a significant negative impact on marine species (7). Widespread agricultural use of fertilisers can cause leaching of nutrients into seawater, causing algal blooms, which can harm other species (16).

Litter washed up from the sea or dropped directly on the shore can also have an adverse effect on marine species (3), with animals becoming entangled in, or even ingesting, items of rubbish. Turtles and seabirds are frequently found to have plastic in their stomachs when examined. Sadly, plastic rubbish on beaches has increased by 135 percent since 1994. Untreated sewage can also upset the balance of the marine ecosystem, with toxins accumulating in shellfish and other animals (17).

Development of coastal areas for storm defence or recreation can have a mixed effect on marine life, as although habitat destruction is likely, development may also allow colonisation of a new habitat (3)(14). Recreational use of shores (including activities such as walking, driving vehicles and burning driftwood) can also disturb marine life (7). Agriculture close to shores may introduce new plant species, which can potentially displace existing ones, while grazing animals such as cattle can adversely affect the native plant species (18).

The predicted rise in sea levels due to climate change could eliminate a large amount of coastal habitat (3)(14). Beaches naturally move inland with a long term rise in sea levels, but human building development, along with a lack of sediment, prevent this from happening, causing ‘coastal squeezing’ where the width of the coast actually decreases (19).

Conservation

There are several conservation initiatives that aim to preserve the British coast. Natural England have designated 1,057 kilometres of the English coastline as ‘Heritage Coast’, meaning that marine species in these areas are protected (20). Marine Protected Areas and Marine Conservation Zones are also the responsibility of Natural England and such areas play an important role in the conservation of the sea and coastline (20)(21)(22)(23).

Get involved

The Marine Conservation Society'sBeachwatch initiative is a great way to help protect your local coastline. Through this scheme you can take part in beach cleans and wildlife surveys (17). Surfers Against Sewage also organise many beach cleans that volunteers can take part in (24). Although hand-cleaning beaches is more time-consuming than mechanical cleaning, it is more environmentally friendly as it does not remove the top layer of rocks, and therefore leaves habitats intact (1).

The MCS’s Good Beach Guide recommends beaches in the UK with the best water quality and lowest water pollution levels. The idea behind this scheme is to encourage local authorities, water companies and businesses to address any marine pollution issues (25). Of course, the public also has a part to play in keeping Britain’s beaches clean. Make sure that you do not leave any litter when visiting beaches and cliffs, and recycle rubbish wherever possible. At home we should all aim to use less water and use environmentally friendly cleaning products, as in doing so we can minimise harmful sewage spills on our coasts (25).

Some of Britain’s best coastal walks are found in Wales. The Pembrokeshire Coast National Park provides many vital rocky shore habitats (as well as important inland woodland) for native species that have disappeared from many areas of the UK. Choughs and skylarks can be seen on cliffs, and on clear days cetaceans may be seen further out to sea.

Glossary

Simple plants that lack roots, stems and leaves but contain the green pigment chlorophyll. Most occur in marine and freshwater habitats.

Cetaceans

A group comprising all whales, dolphins and porpoises.

Crustaceans

Diverse group of animals with jointed limbs and a hard external skeleton, characterised by the possession of two pairs of antennae, one pair of mandibles (mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, woodlice and barnacles.

Intertidal

Pertaining to the intertidal zone, the region between the high tide mark and low tide mark.

A composite organism made up of a fungus in a co-operative partnership with an alga. Owing to this partnership, lichens can thrive in harsh environments such as mountaintops and polar regions. Characteristically forms a crustlike or branching growth on rocks or tree trunks.

Sublittoral

A marine zone between the low water mark and depths of around 200 metres.

Littoral zone

The shallow marine zone where light reaches the substrate; this zone is subject to submersion and exposure by tides.

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